Pretensioners are known which use a power operated device having a piston which is mounted within a cylinder and is driven by an ignitable charge to travel in a first direction and to pull a connecting member which is usually an attached, flexible member such as a cable to remove safety belt slack in the occupant restraint system. More specifically, the slack is removed by the cable, which is usually attached to a buckle part of a three-point buckle system in a downward direction to tighten the safety belt about the passenger. The power operated device includes a pyrotechnic gas generator which drives a piston attached to the cable forwardly to travel the necessary distance to remove the slack from the seat belt system. The pretensioner includes a cable deflection device which changes the direction of cable travel from a generally vertical direction at the buckle to a generally horizontal direction of travel for the cable end attached to the piston traveling in a horizontally disposed cylinder. When the piston has traveled to the full extent of its travel and has taken out the slack, the pretensioner will have pulled the person down on the seat and thereafter the person and the attached belt system begin to rebound upwardly.
To prevent the passenger from rebounding and returning slack into the seat belt system, a one-way locking mechanism is provided to resist the opposite direction rebound travel of the cable such as disclosed in U.S. Pat. No. 6,213,513. As shown in this patent, the gas generator and the deflection device of the pretensioner include metal castings of complex shapes which add considerably to the cost of the pretensioner device and it is desired to eliminate the casting to reduce the cost of pretensioners. A pretensioner constructed without such a complex casting is disclosed in U.S. Patent Application Publication No. 2003/0030263; but in this pretensioner a tubular cylinder member has a piston with a locking device in the cylinder and an integral end portion of the cylinder bent at an acute angle and sized and shaped to hold a gas generator therein. Moreover, in most of these pretensioners the one-way clutch or one-way locking device for the cable is provided within the cylinder and is positioned on the piston and is cooperable with the cylinder wall. The cylinder must be made strong enough to transfer these forces from the piston and cable during the passenger's rebound pulling on the cable through the locking device and the cylinder to the pretensioner's anchorage on the vehicle. These cylinders usually have grooves serrations, or the like on their interior walls that cooperate with balls or other one-way locking components on the piston.
There is a need to simplify the pretensioner construction in order to reduce its cost and there is also a need to provide a simplified seat belt pretensioner in both the number of components and their assembly. Usually, these seat belt pretensioners are relatively large and costly, hence, there is a need to provide a slim profile and low cost pretensioner that provides not only a cost advantage but also provides a packaging advantage. There is simply not much space about the seats of a vehicle of various kinds to install a pretensioner and to attach it to the vehicle floor or to the seat. Thus, a slim profile for the pretensioner is desirable. Different vehicle specifications and/or different OEMS will require various sizes of charges and gas generation forces and it is desirable to be able to have a pretensioner that can provide such variable charges in an easy manner.